RESUMO
BACKGROUND: Studies in the human term placenta have shown that muscarinic cholinergic receptors M1-M4 are located in the sincitiotrofoblasto in the basement membrane and in the brush border membrane of the villi. However, in both studies the methodology has not been implicated microscopy methods to reveal its location. OBJECTIVE: To determine the expression of muscarinic cholinergic receptors M1 and M2 in human term placenta. MATERIALS AND METHODS: We analyzed 20 samples of human placenta at term newborns. Muscarinic cholinergic receptors M1 and M2 were detected by immunohistochemistry and polyclonal antisera. The optical density of the signal for each muscarinic cholinergic receptor was analyzed with Image Pro Plus software. 30 readings were made by the placenta (n=600). The expression of muscarinic cholinergic receptors were analyzed using the Student t test. RESULTS: The expression of muscarinic cholinergic receptors M1 and M2 in human term placenta were found in the sincitiotrofoblasto of secondary and tertiary villi. The expression of muscarinic cholinergic receptors M1 and M2 in the population showed that the RCM M2 is expressed in a greater proportion than RCM M1 (p < 0.01). The expression of muscarinic cholinergic receptors M1 and M2 was lower in newborns with low weight for gestational age, although the difference was not significant (p > 0.05). CONCLUSIONS: The expression of muscarinic cholinergic receptors were identified in placental sincitiotrofoblasto predominantly M2 muscarinic cholinergic receptor. The values reported here represent a baseline that can be used to analyze the expression of muscarinic cholinergic receptors in the placenta of women with a history of environmental exposure to toxic substances.